Heh, I debated putting a second paragraph about this. And yes, while it's not like they're paying the entire cost of developing a car from scratch each time, there's still a lot of duplication of work.
They still have a fair number of unique parts, they still have a fair amount of individual development and certification, they still have their own parts supply chains… these all add costs compared with literally having the same vehicle.
It's not that I see no reason to have multiple marques—after all, there is meaningful differentiation between the different VW ones, for example. But at some point you've got to stop and ask when you have too many.
They still have a fair number of unique parts, they still have a fair amount of individual development and certification, they still have their own parts supply chains… these all add costs compared with literally having the same vehicle.
It's not that I see no reason to have multiple marques—after all, there is meaningful differentiation between the different VW ones, for example. But at some point you've got to stop and ask when you have too many.